Reduced physical activity during submarine deployment: health and performance consequences and feasible countermeasures — a narrative review

OBJECTIVES: Submarine environments pose unique challenges to maintaining physical activity due to space constraints, operational demands, and prolonged confinement. This review aims to synthesize existing literature on the health and performance consequences of reduced physical activity in submarine personnel and to examine feasible strategies to mitigate these effects during deployment. METHODS: A narrative overview methodology was adopted, with peer-reviewed studies identified from PubMed, Scopus, and Google Scholar. Articles examining physical activity patterns, health outcomes, and exercise or movement-based interventions in submarine environments and comparable confined operational settings were included. RESULTS: Submarine deployments are consistently associated with reduced physical activity, low step counts, and limited opportunities for structured exercise. Prolonged inactivity during deployment may contribute to unfavorable changes in body composition, including increases in fat mass, potential reductions in muscle mass, and in some contexts, alterations in bone health. Collectively, these changes may increase longer-term cardiometabolic and musculoskeletal risk, particularly with repeated deployments. Practical, low-burden strategies such as increasing daily movement, no-load or bodyweight resistance exercise, and minimal-dose eccentric-focused training appear feasible within submarine constraints and may help preserve health and physical function. CONCLUSIONS: Maintaining physical health during submarine deployments requires proactive, context-specific approaches compatible with the operational environment. Low-resource exercise strategies that emphasize maintenance of activity, rather than performance optimization, may provide a practical means of mitigating health and performance declines during deployment. Further research is needed to determine the long-term effectiveness and implementation of these approaches in submarine populations.